1. Field of the Invention
The present invention relates to electronic apparatus, typically solid state radio receivers, wherein means have been provided for reducing the costs of supplying low voltage power from higher voltage a.c. mains. The invention also relates to regulated power supplies. The techniques disclosed are suitable for use with integrated circuits (IC) apparatus.
2. Description of the Prior Art
Power supplies for solid state receivers tend toward simple low cost configurations. A typical configuration is a half wave rectifier operating through a voltage dropping resistance, and including a single large filter capacitor at the output terminal of the rectifier. If the single section filter has too great a "hum" component, a second RC section may be provided. If the series resistance used to reduce the voltage from a typical value of 110 volts to 12 volts occasions too large a fluctuation in the output voltage under normal manufacturing variations and ambient conditions, then a transformer supply, which is of higher cost, or voltage regulator may be necessary. The need for voltage regulation is normally set by the tolerance of the equipment to increases in supply voltage. If the equipment uses large valued, low voltage capacitors, then there is a cost trade-off between increasing the voltage rating of the capacitor to preclude failure from over voltage versus adding a voltage regulation feature. The integrated circuit process also sets an upper limit to the tolerable supply limits. IC processors are frequently defined as 14 volt, 16 volt, 20 volt, 25 volt, etc. processes. The higher the voltage, the more costly they are, so the tendency is to reduce the processes to the lower voltage ranges consistent with circuit performance. The advent of integrated circuitry has made it practical to add active elements to a configuration with only the modest incremental costs of additional chip area. Since zener voltage reference devices and large area transistors can both be integrated, adding one internal regulator now becomes an alternative to the other measures noted above.